Effects of Anion Identity and Concentration on Electrochemical Reduction of CO2

Resasco, J., Lum, Y., Clark, E., Zeledon, J., Bell, A. T.  Effects of anion identity and concentration on electrochemical reduction of CO2. ChemElectroChem, DOI: 10.1002/celc.201701316 (2018).


Scientific Achievement

Hydrogen-containing anions (HSO4-, HCO3-, HBO3-, H2PO4-) buffer the electrolyte against the effects of concentration polarization (e.g., a rise in cathode pH) and provide a source of H atoms for CO2 reduction via reactions such as HCO3- + e- → H* + CO3^2-.

 

Significance & impact

By choice of electrolyte anions with a high pKa, product selectivity can be shifted from H2 and CH4 to C2 products.

Research Details


  • An investigation was conducted of the effects of bicarbonate buffer concentration and the composition of other buffering anions on the partial currents of the major products formed by reduction of CO2 over Cu.Discrete (Ni-La-Co-Ce)Ox coatings were synthesized on a uniform BiVO4 thin film yielding 858 catalyst/BiVO4 assemblies with 3 different catalyst loadings.

Contact: alexbell@berkeley.edu

Read More Research Highlights

    Reprinted from Resasco, J., Lum, Y., Clark, E., Zeledon, J., Bell, A. T.  Effects of anion identity and concentration on electrochemical reduction of CO2. ChemElectroChem, DOI: 10.1002/celc.201701316 (2018).   The influence of anion composition for electrolytes prepared from potassium salts on the current densities for H2, CO, HCOOH, CH4, C2H4, and C2H5OH shown as a function of cathode potential. The strong variation in the current densities for H2 and CH4 formation for a given potential on the RHE indicates that the formation of these products is rate-limited by the provision of H atoms from the anions to the carbon-containing species on the catalysts.  The near absence on an effect of anion composition on the dependence of the current density for forming HCOOH, CH4, C2H4, and C2H5OH for a given cathode potential on the SHE scale indicates that the formation of these products is not rate-limited by the supply of H atoms from anions of H2O to species adsorbed on the cathode.

 

Reprinted from Resasco, J., Lum, Y., Clark, E., Zeledon, J., Bell, A. T.  Effects of anion identity and concentration on electrochemical reduction of CO2. ChemElectroChem, DOI: 10.1002/celc.201701316 (2018).

The influence of anion composition for electrolytes prepared from potassium salts on the current densities for H2, CO, HCOOH, CH4, C2H4, and C2H5OH shown as a function of cathode potential. The strong variation in the current densities for H2 and CH4 formation for a given potential on the RHE indicates that the formation of these products is rate-limited by the provision of H atoms from the anions to the carbon-containing species on the catalysts.  The near absence on an effect of anion composition on the dependence of the current density for forming HCOOH, CH4, C2H4, and C2H5OH for a given cathode potential on the SHE scale indicates that the formation of these products is not rate-limited by the supply of H atoms from anions of H2O to species adsorbed on the cathode.